This is a myth: in Germany, as in many other countries, copyright covers only specific expression; you cannot copyright either the name of a historical person or a topic of discourse. The videos were briefly taken down as an automatic response to a complaint, but it seems the complaint was not upheld and the videos were restored.

At the time, Germany had a law censoring insulting comments about foreign heads of state, but that only applied to living ones (and maybe only those in office at the time?) That law was repealed in 2018.

The videos remained blocked in Turkey, but on account of a specific law banning criticism of Ataturk, not copyright.

Okay, how this changes the core argument? The videos were not taken down briefly because they did not comply with the Turkish law that protects Ataturk from defamation but for the claim that they violated someones commercial interests.